In automotive transmissions using position-controlled input clutches, such as a dual clutch transmission (DCT) or an automated manual transmission (AMT), synchronizers are used to engage drive gears so as to achieve a desired gear ratio. A synchronizer typically includes a hub that is fixedly mounted to a shaft of the transmission, as well as a sleeve that is engaged with the hub. During a synchronization event prior to engagement of an input clutch, the sleeve is moved via translation of a corresponding shift fork. Axial movement of the fork urges the sleeve along a shaft axis, across a blocker ring, and into interlocking engagement with a particular drive gear, with the drive gear depending on the particular shift maneuver being commanded. The timing, position, and movement of the various forks and synchronizers in a transmission are precisely controlled in order to obtain consistently smooth gear shifts.
In a DCT in particular, a first input clutch is applied to engage oddly-numbered gears of a gearbox, i.e., 1st, 3rd, 5th, and 7th gear, while a second input clutch is applied to engage the evenly-numbered gears such as 2nd, 4th, 6th, and reverse gear. Different forks are used to move synchronizer sleeves for each of these gears. A transmission control module (TCM) typically predicts the next-selected or desired gear using various available control inputs such as engine acceleration and braking levels. The TCM then commands engagement of a particular synchronizer and fork ahead of engagement of the input clutch needed for establishing a driving connection between the engine and the selected drive gear. The unique structure of a DCT can provide faster shift speeds relative to a conventional automatic transmission, with improved overall shift control and increased power.